Signaling system



ci. z8. 1924 1,512,930

H. W. HITCHCOCK SIGNA'LING SYSTEM Filed UOt 20. 1921 may Patented Unt. 28, 1924.

TES!

Artnr lo Fricaft HARRY w. HITCHCOCK, or NEW YORK, N. AssieNon To AMERICAN 'rnnnrnonil AND TnLnenArH COMPANY, a CORPORATION or NEW YORK,

SIGNALING SYSTEM.

Appiicatipn mea october 2o, 192i.' sei-iai No. 508,946.

To all Mahomet may concern:

Be it known that I, HARRY W. HITCHCOCK,

residing at New York, in the county of Bronx and State of New York, have invented certain Improvements in Signaling Systems, of which the following is a speciiication. l

This invention relates to signaling systems and particularly toa method and means for constructing a cable from a plurality of sections in order to minimize the effect upon transmission ,of signals caused by irregularities in the impedance of the various sections of which the cable is composed. In balancing a cable it is, of course, necessary to make detailed adjustments of the balancing network to match the irregularities in the cable, and my invention involves the systematic arrangement of the sections of the cable so that the adjustment of the balancing network is facilitated.

In the construction of long cables such, for example, as a long submarine cable, it is necessary to `manufacture the cable in relatively short sections and to splice the vari- -ous sections together in Order to produce the complete cable. Although such cables are designed to have a definite impedance value it is well known that the various sec tions will differ in varying degrees, due to various factors in the process of manufacture of a cable.

It is the object of this invention to provide a method and means Vfor splicing together the various sections of a cable in order to produce a complete cable which will offer the least vinteri'erence with transmission, due to the impedance irregularities of the Various sections of which the completed cable is composed.

This invention will be better understood from the following description when read in connection with the attached drawing, of which Figure 1 represents for example nine sections approximately equal in length which form one-half of thecompleted cable. Fig. 2 shows graphically the arrangement of these sections with respect to their per cent deviation from the average impedancevalue of the entire half length of completed cable, and Fig. 3 shows graphically the effect produced'upon the impressed signaling voltage by the arrangement of the sections of ycable as shown in Fig. 2.

Upon the completion of the' manufacture Aof all the sections of cableforan entire cable that is intended to extend between two points, the impedance of each section of cable is measuredand the average value for each half length, thatis to say, "thejdist'ance' from each terminusy to the midpoint, is ob,-

tained. For thepurpose of describingthis invention, I have shown'in Fig. 1 nine sec# tlonsdesignated l to 9 inclusive, whiclirepresent for example one-half the length of the entire cable that extends from one-ten' minus to the midpoint of f,the saidcable. Section No. 1 represents thatfnearest the terminus of this -half length 4of 'cable'r and the other Sectionsl have been numbered con secutively yin the direction extending away from the lsaid terminus@ The yorder fof ,an rangement of these sections depends upon their impedance, which should be deter-l mined by the quantity grwhere `L and C represent respectively the inductance fand capacity of the sections. In this determina.'-` tion the resistance and llea'kagevmay bedisregarded, since for the important parttof'y the telephone frequency range their effects on the impedance alge relatively small.

When the quantity ihas been obtained for all ythe sectionsof `caloleintended tocdnstitute the half .length of' completed ycable from one terminus to vthe -midpoint (if the said cable, the average value of -for this'entire rhalf length of Icab'leshould befob-` c tained,'and the percentage by which each lsec-v fromthis selected section of cable shouldbe obtained. VThe other sections of ,cable shouldgtlien be selected and joined together in accordance with the magnitude 'of 'their deviation yfrom the average, the section havingthe least deviation being connected with aol the terminating 'section and the section having the greatest deviation being placed at the point most remote from the terminating section, viz, at the midpoint of the coin4 pleted cable.' 'Thus, the distance of a particular section of cable from the terminus of, the cable will depend upon the relative value of its impedance deviation to the average value of the entire half length of cable. Furthermore, since the impedance of approximately one-half of the entire number of sections will be above thevaverage and the other half below the average, the consecutive sections should not only 'be arranged sovthat their impedance; deviation will increase fromthe terminus outward toward the center'of the cable but the adjacent sections should alternatepositively and negatively from the average value. This is clearly shown in Fig. 2, invwhich the terminating section, No.1, is shown asvhaving the value of unity and the adjacent section, 2, having theA value of of 1% above No. l. The subsequent pairs of sections, 4L and 5, 6 and '7, 8 and 9, are each made up ot sections having respectively positive and negative deviations of the same magnitude. These deviations are assumed but they serve to illustrate the principle upon which this invention is based. In a similar manner the other half length of cable is built up so that the section of minimum 4deviation is at the distant terminus, and the sections of maximumkdeviation are at the midpoint of the cable. It will be apparent, therefore, that the completed cable tapers in impedance deviation from the midpoint in both directions to the two terminals of the cable.

i For the frequencies within the telephone range, such an arrangement of lengths produces the minimum deviation from the average impedance since the lengths are short enough so that the phase diiference, due to the impedance irregularities of successive sections, when viewedv from each terminal of the cable is small. This is clearly shown in Fig. 3. In this figure fo represents the limiting frequency for the necessary voice range for telephoning; and (a) represents the eifectiveresistance of a cable whose sections are uniform and have a value of J@ distance from the input end. Although the actualdeviations of the sections 6 and 7 are greater than those of 2 and 3 the attenuation of the cable between the sending end and their position reduces their effect upon the sending end impedance. .It is obvious that if 2 and 3 or 6 and 7 were of the same sign the combined eiect of the two would be approximately twice as great as either taken alone. Also the more nearly 2 and k3 are equal in magnitude the smaller will be the resultant 23. This average cannot become zero owing to the fact that sections 2 and 3 are not equidistant from the'input end. The eiiect of this is to make the requencies l2 and 13 at which the curves 2 and 3 cross the frequency axis different. These frequencies approach each other and also become higher as the length of the sec'- tions is reduced. Hence by decreasing the length of the sections a better balance may be secured. lithin the range of frequencies represented by the voice, there is but a slight phase difference due tothe difference.

in position of successive sections and consequently the effect on transmission will be small. y

Although this invention has been disclosed in 'a certain form it is not intended to limit it to this particular form since it is capable of embodiment in otherr forms within the spirit and scope of the appended claims.`

-l/Vhat is claimed is: f

l.. ln a signaling system, the method of constructing a cable comprising a plurality of sections, which consists in measuring the impedance of each of the said sections, obtaining the average impedance of all the sections measured, arranging the sections in such order that the section at each terminus shall have the value nearest the average, and arranging they subsequent pairs of adjacent sections between each terminus and themidpoint of the cable in the order of increasing deviation, the adjacent sections of each pair havingV approximately equal positive Aand negative deviations. i

2. Tn a signaling system, the method of constructing a cable comprisinga plurality value of each of th said sections, obtaining of sections, which consists in measuring the average of i6 value for all the sections measured, arranging the sections. .in such order that the section at each terminus shall have L f value nearest the average,

llO

constructing a cable comprising a plurality of sections, which consists in measuring the impedance of' each of the sections, obtaining the average impedance of all the sections measured, arranging the sections in such order that the section at each terminus shall have the value nearest the average, and arranging the subsequent pairs of adjacent sections in the order of increasing deviation from the average, the adjacent sections of each pair having approximately equal positive and negative deviations.

5. A cable comprising a plurality of sections, the impedances of which deviate uniformly from the average value for all sections in the direction away from the terminal sections of the said cable.

6. A cable comprising a plurality of sections so arranged that each terminal vsection shall have an impedance approximating the average impedance of all the sections extending between each respective terminal and the midpoint of the saidcable, and the subsequent pairs of sections of each half section of the cable shall increase in imped ance in the direction away from each terminal section, the adjacent sections of each pair having approximately equal positive and negative deviations from the average. c

7. A length of submarine cable comprising a plurality of sections in series, theterminal section to which signaling instru ments are to be connected having an im* pedance which is about the average of that pluralityiof sections in series, the terminal n section to which signaling instruments are to beconnected having an impedance Which A,is about the yaverage of that of all of said sections, fand theremaining sections from said terminal section toward the other terminal having values of impedance alternately higher and loWer than that of said terminal section, the difference between the impedance ofV eachsection and that of said terminal section being progressively greater'in the directionr away from said terminal section.

9. The method of constructing a signaling cable comprising a plurality off sections in series, which comprises measuring the impedance of each of a plurality of sections and arranging them With a section ofA about average impedance at a termina-l to Which signaling "apparatus is to be connected and with sections of high and low values of impedance in alternation successivelyv alongthe cable for at leasta part of its length.

In `testimony whereof, I have signed my name to this speciication this 18th day of October, 1921.

HARRY W. HITCHCOCK.' 

